Câu hỏi của Dũng Lê

Question

20 Rút gọn

a) (2x-y)(2x+y)-(2x+y)^2  ;   b) (x-3)(x^2+3x+9)-(5-x)^2

c) (2x+y)(4x^2-2xy+y^2)-(2x+y)^3    ;   d) (3x-5)^2-(3x+5)^2

lê thị hương giang · Accepted Answer

$a,\left(2x-y\right)\left(2x+y\right)-\left(2x+y\right)^2$

$=4x^2-y^2-4x^2-4xy+y^2$

$=-4xy$

$b,\left(x-3\right)\left(x^2+3x+9\right)-\left(5-x\right)^2$

$=x^3-27-25+10x-x^2$

$=x^3-x^2+10x-52$

$c,\left(2x+y\right)\left(4x^2-2xy+y^2\right)-\left(2x+y\right)^3$

$=8x^3+y^3-4x^2-4xy-y^2$

$d,\left(3x-5\right)^2-\left(3x+5\right)^2$

$=\left(3x-5-3x-5\right)\left(3x-5+3x+5\right)$

$=-10.6x=-60x$Câu trả lời: $a,\left(2x-y\right)\left(2x+y\right)-\left(2x+y\right)^2$